Adds the `uid` and `gid` settings in the main configuration file, which
allows weblug to run under a unprivileged user account. This comes with
the limitation, that unless the program runs as root, custom webhook
`uid/gid` settings are not possible.
Adds the `basic_auth` section in a webhook that allows to define a
required username/password for being able to access a given webhook.
Signed-off-by: phoenix <felix@feldspaten.org>